JPH03137147A - Insulating resin composition having excellent water resistance - Google Patents

Abstract

PURPOSE:To obtain a water-resistant insulating resin composition having stable bond strength to metal by blending a mixed resin of an acid modified material of ethylene-ethyl acrylate copolymer and straight-chain low-density polyethylene with carbon black. CONSTITUTION:(A) 100 pts. wt. acid modified material having 0.05-12 wt.% acid content prepared by subjecting an ethylene-ethyl acrylate copolymer having preferably 1-30 wt.% ethyl acrylate content to graft polymerization with an unsaturated carboxylic acid is blended with (B) 50-150 pts. wt. straight-chain low-density polyethylene to give 100 pts. wt. base resin having 0.05-30 g/minute, preferably 0.1-3 g/minute melt index, which is mixed with (C) 2-15 pts. wt., preferably 3-8 pts. wt. carbon black (preferably ketjenblack) to give an insulating resin composition having excellent water resistance suitable for water barrier tape for water barrier electric cable, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a resin composition with excellent water resistance, and more specifically, to a resin composition that has stable adhesion to metals over a long period of time and is suitable for use in water-blocking cables. The present invention relates to a resin composition useful as a material for water-blocking tape.

(Prior Art) When moisture enters the insulator of a rubber/plastic electric cable, a water tree is generated within the insulator due to the superposition of this moisture and the electric field, which causes the breakdown of the electric cable. In the case of communication cables, ingress of water from the outside can reduce the insulation properties of the insulator, leading to interference.

For this reason, in polyethylene sheathed insulated cables that require water-blocking properties, for example, water-blocking tape made by laminating metal foil such as lead foil and adhesive plastic film is bonded directly below the sheath layer. A water-blocking capeple has been developed. In the case of this water-shielding cable, it is important that the lead foil and adhesive plastic film maintain strong and stable adhesion over a long period of time even if the cable is submerged in water.

Conventionally, in such waterproof tapes, materials for the film laminated with metal foil include, for example, polyethylene, polypropylene, polybutene, ionomer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and isopropylene. One or more of rubber, acrylonitrile butadiene rubber, and styrene butadiene rubber are used.

However, these materials have problems in that their adhesion to metal foil is insufficient and their heat resistance is also poor.

Therefore, recently, insulating resin compositions (for example, GA-0 manufactured by NUC Co., Ltd.
04) has been developed, and a water-blocking tape in which a film of this resin composition and metal foil are laminated has been proposed.

(Problems to be Solved by the Invention) However, the above-mentioned resin composition is processed to a thickness of 10 to 30 mm by a method such as T-die extrusion or inflation extrusion.
0μm film, and this film has a thickness of 10-10
If a composite tape made by laminating 0 μm metal foil such as lead foil, aluminum foil, copper foil, or stainless steel foil with a hot pressure roll is immersed in hot water at 70°C for a long period of time, the metal will change. A problem arises in that the adhesion between the foil and the film is reduced. That is, the above-mentioned resin composition itself cannot be said to have the water resistance required for a water-blocking tape.

The present invention provides water resistance that significantly improves the adhesive strength with metal foil without impairing the other properties of the resin composition described above, and does not cause a decrease in the adhesive strength with metal foil even when immersed in hot water. The purpose is to provide an excellent insulating resin composition.

(Means and effects for solving the problem) In order to achieve the above-mentioned object, in the present invention, a mixed resin of an acid-modified ethylene-ethyl acrylate copolymer and linear low-density polyethylene is used as a base resin. year,
2 parts of carbon black per 100 parts by weight of the base resin
There is provided an insulating resin composition with excellent water resistance, characterized in that the composition contains 15 parts by weight of the above compound.

The insulating resin composition of the present invention includes a base resin and carbon black as essential components, which will be described later.

First, the base resin is composed of a mixture of an acid-modified ethylene-ethyl acrylate copolymer and linear low-density polyethylene.

The acid-modified ethylene-ethyl acrylate copolymer used may be any product obtained by graft polymerizing an unsaturated carboxylic acid to an ethylene-ethyl acrylate copolymer, and is not particularly limited.

As the ethylene-ethyl acrylate copolymer, it is preferable to use one whose ethyl acrylate content is 1 to 30% by weight. Those with an ethyl acrylate content of less than 1% by weight have excellent strength and heat resistance, but
However, the initial adhesion strength with the metal foil decreased significantly, and
If the amount is greater than % by weight, the initial adhesive strength with the metal foil is excellent, but not only the film formation but also the strength and heat resistance are significantly reduced. A particularly preferred range of ethyl acrylate content is 3 to 15% by weight.

Examples of unsaturated carboxylic acids to be graft-polymerized to the ethylene-ethyl acrylate copolymer include unsaturated basic acids such as acrylic acid and methacrylic acid; maleic acid, oleic acid, fumaric anhydride, fumaric acid, and itaconic acid; Unsaturated dibasic acids such as Each of these may be used alone, or two or more types may be used in an appropriate combination.

The acid content expressed by the amount of the unsaturated carboxylic acid present in this modified product is 0.05 to 12% by weight, preferably 0.5 to 5% by weight, particularly preferably 0.2 to 1% by weight.
controlled within the range of

If the acid content is less than 0.05% by weight, when it is made into a film and laminated to metal foil, the adhesion to the metal foil is insufficient, and if it exceeds 12% by weight, it cannot be made into a film. Film forming properties at the time.

This is because the smoothness, uniformity, etc. of the film surface deteriorate.

Linear low-density polyethylene, which is another component of the base resin, is a component that contributes to improving the film processability, heat resistance, and water resistance of the obtained resin composition.

The linear low-density polyethylene to be used is not particularly limited, but when mixed with the acid-modified product of the ethylene-ethyl acrylate copolymer described above, it does not reduce the adhesiveness of the acid-modified product, and It is preferable that the resin composition has good compatibility and can improve the heat resistance and film processability of the resulting resin composition.

The blending ratio of the linear low density polyethylene is preferably 50 to 150 parts by weight based on 100 parts by weight of the acid-modified ethylene-ethyl acrylate copolymer. If this blending ratio is out of the above range, the film strength
This is because, at the same time as the heat resistance decreases, the stability of film formation during film formation and the rewinding property of the formed film also deteriorate.

The base resin is obtained by mixing the above two components. The melt index of the mixed resin in that case is determined by considering film processability, heat resistance, strength of the obtained film, etc., but is usually 0.05 to 30 g/min,
More preferably, it is controlled to 0.1 to 3 g/min.

The flame-retardant resin composition of the present invention is prepared by blending carbon black with the above base resin.

When carbon black is blended into the base resin, the adhesive strength of the resulting resin composition is prevented from decreasing during immersion in hot water. The reason for this is not clear, but
The blended carbon black has water-retentive properties, which prevents moisture that has entered the water-blocking tape from the outside from penetrating directly into the interface between the metal foil and the film adhesive of the resin composition. It is thought that part of the black color is due to the fact that it prevents the formation of an oxide film on the surface of the metal foil and reduces its wettability.

The carbon black used is not particularly limited, but for example, Ketchien Black EC (trade name of carbon black manufactured by Akzo Corporation) is suitable because it shows a large effect even when added in a small amount. Of course, acetylene black, furnace black, etc. can also be used.

The blending amount of carbon black is set in the range of 2 to 12 parts by weight based on 100 parts by weight of the base resin. If the blending amount is less than 2 parts by weight, no effect of improving the adhesive strength between the obtained resin composition film and metal foil will be exhibited at all in the water-blocking tape laminated with the film of the resin composition, and if it exceeds 12 parts by weight, This is because the film begins to become conductive. The preferred blending amount of carbon black is 100% of the base resin.
The amount is 3 to 8 parts by weight.

In addition, the resin composition of the present invention may further contain, if necessary,
Stabilizers such as antioxidants and UV absorbers.

Appropriate amounts of lubricants, inorganic fillers, surfactants, antistatic agents, copper damage inhibitors, flame retardants, blowing agents, plasticizers, etc. may be added.

(Examples of the invention) Example 1 Acid-modified product of ethylene-dityl acrylate copolymer with ethyl acrylate content of 9% by weight with maleic acid (acid content: 0.5% by weight) and 50% by weight of low-pressure method. A mixed resin was prepared by mixing with 50% by weight of density polyethylene.

Add 100 parts by weight of this mixed resin to Ketchen Black EC (
3.0 parts by weight (manufactured by Akzo Corporation) was blended to prepare an insulating resin composition having a volume resistivity of 1011 Ω-2.

Using this resin composition, a film was formed to a thickness of 100 μm by an inflation method, and the obtained film was laminated on both sides of a copper foil having a thickness of 50 μm using a hot roll.

The peel strength between the film and the lead foil in the obtained laminate tape was measured. Next, this laminate tape was immersed in hot water at 70° C. for 240 hours and then taken out, and the peel strength between the film and the lead foil was also measured. The above results are shown in Table 1.

Example 2 A laminate tape was produced in the same manner as in Example 1, except that aluminum foil with a thickness of 50 μm was used instead of lead foil. The peel strength of this laminate tape was also measured in the same manner as in Example 1.

The results are shown in Table 1.

Example 3 Furnace Black 1 instead of Ketchen Black EC
0 parts by weight, and the thickness was 50% by extrusion method with a T-die.
A laminate tape was produced in the same manner as in Example 1, except that a μm film was formed. The peel strength of this laminate tape is shown in Table 1.

Comparative Example 1 Without Ketchen Black EC, volume resistivity was x
A laminate tape was produced in the same manner as in Example 1, except that a mixed resin having a resistance of olsΩ-■ or higher was used. The peel strength of this laminate tape is shown in Table 1.

Comparative Example 2 A laminate tape was produced in the same manner as in Example 1, except that the amount of Ketchen Black EC was 1.5 parts by weight. The peel strength of this laminate tape is shown in Table 1. Incidentally, the volume resistivity of the film in this case was 1018 Ω-b.

Comparative Example 3 A laminate tape was produced in the same manner as in Example 1, except that the amount of Ketchen Black EC was 20 parts by weight. The peel strength of this laminate tape is shown in Table 1. The film in this case had a volume resistivity of 106 Ω-cm and exhibited semiconductivity, and the laminate tape could not be used as a water-blocking tape.

Table 1 (Effects of the Invention) As is clear from the above explanation, when the insulating resin composition of the present invention is formed into a film and laminated with metal foil, the initial adhesive strength with the metal foil is lower than that of the conventional one. It has the advantage that its adhesive strength does not decrease even if it is immersed in warm water for a long time. Therefore, the resin composition of the present invention is extremely useful as a material for a water-blocking tape incorporated into a water-blocking capeple.

Claims (1)

[Claims] The base resin is a mixed resin of an acid-modified ethylene-ethyl acrylate copolymer and linear low-density polyethylene, and 2 to 15 parts by weight of carbon black is blended with 100 parts by weight of the base resin. An insulating resin composition with excellent water resistance.